title: HOXB7 mRNA is overexpressed in pancreatic ductal adenocarcinomas and its knockdown induces cell cycle arrest and apoptosis.
abstract: BACKGROUND
  Human homeobox genes encode nuclear proteins that act as transcription factors involved in the control of differentiation and proliferation. Currently, the role of these genes in development and tumor progression has been extensively studied. Recently, increased expression of HOXB7 homeobox gene (HOXB7) in pancreatic ductal adenocarcinomas (PDAC) was shown to correlate with an invasive phenotype, lymph node metastasis and worse survival outcomes, but no influence on cell proliferation or viability was detected. In the present study, the effects arising from the knockdown of HOXB7 in PDAC cell lines was investigated.
  
  
  METHODS
  Real time quantitative PCR (qRT-PCR) (Taqman) was employed to assess HOXB7 mRNA expression in 29 PDAC, 6 metastatic tissues, 24 peritumoral tissues and two PDAC cell lines. siRNA was used to knockdown HOXB7 mRNA in the cell lines and its consequences on apoptosis rate and cell proliferation were measured by flow cytometry and MTT assay respectively.
  
  
  RESULTS
  Overexpression of HOXB7 mRNA was observed in the tumoral tissues and in the cell lines MIA PaCa-2 and Capan-1. HOXB7 knockdown elicited (1) an increase in the expression of the pro-apoptotic proteins BAX and BAD in both cell lines; (2) a decrease in the expression of the anti-apoptotic protein BCL-2 and in cyclin D1 and an increase in the number of apoptotic cells in the MIA PaCa-2 cell line; (3) accumulation of cell in sub-G1 phase in both cell lines; (4) the modulation of several biological processes, especially in MIA PaCa-2, such as proteasomal ubiquitin-dependent catabolic process and cell cycle.
  
  
  CONCLUSIONS
  The present study confirms the overexpression of HOXB7 mRNA expression in PDAC and demonstrates that decreasing its protein level by siRNA could significantly increase apoptosis and modulate several biological processes. HOXB7 might be a promising target for future therapies.
authors.affiliation: Laboratory for Cellular and Molecular Endocrinology (LIM-25), University of São Paulo Medical School, Av, Dr, Arnaldo, 455 # 4305, São Paulo, SP, 01246-903, Brazil. rrgiorgi2@hotmail.com.
authors.forename: Thais
authors.initials: T
authors.lastname: Chile
authors.forename: Maria Angela Henriques Zanella
authors.initials: MA
authors.lastname: Fortes
authors.forename: Maria Lúcia Cardillo
authors.initials: ML
authors.lastname: Corrêa-Giannella
authors.forename: Helena Paula
authors.initials: HP
authors.lastname: Brentani
authors.forename: Durvanei Augusto
authors.initials: DA
authors.lastname: Maria
authors.forename: Renato David
authors.initials: RD
authors.lastname: Puga
authors.forename: Vanessa de Jesus R
authors.initials: Vde J
authors.lastname: de Paula
authors.forename: Marcia Saldanha
authors.initials: MS
authors.lastname: Kubrusly
authors.forename: Estela Maria
authors.initials: EM
authors.lastname: Novak
authors.forename: Telésforo
authors.initials: T
authors.lastname: Bacchella
authors.forename: Ricardo Rodrigues
authors.initials: RR
authors.lastname: Giorgi
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D021441:Carcinoma, Pancreatic Ductal / Q000235:genetics* / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050684:E2F Transcription Factors / Q000235:genetics; D018628:Gene Dosage; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger; D034741:RNA, Small Interfering / Q000235:genetics; D015203:Reproducibility of Results; D016160:Retinoblastoma Protein / Q000235:genetics
chemical_list: D050684:E2F Transcription Factors; C490538:HOXB7 protein, human; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016160:Retinoblastoma Protein